Treatment of keratinous substrates

ABSTRACT

A process for the modification of monomer-pretreated keratinous substrates which comprises treating the keratinous substrate with a small but effective amount of a compound selected from the group consisting of phenyl, mono- and di-isocyanates and phenyl, mono- and di-thioisocyanates.

United States Patent Giuseppe Anzuino Vercelll, Italy;

Clarence Ralph Robbins. Piscataway. NJ. 2.942

Jan. 14, 1970 Nov. 9. I97] Colgate-Palmolive Company New York, N.Y.

Inventors Appl. No. Filed Patented Assignee TREATMENT OF KERATINOUS SUBSTRATES 11 Claims, No Drawings US. Cl 8/1275. 8/1275]. 8/128 Int. Cl 006m 3/00, D06m 3/02, D06m 13/00 Field of Search 8/l27v5,

127.5].128, DIG. l8; 260/855 M; 424/7l Primary E.\'umim'r-Ge0rgc F. Lesmes Asxislun! Examiner-B. Bettis Almrneyx-Herbcrt 5. Sylvester. Murray M. Grill. Norman Blumenkopf. Ronald S. Cornell. Robert A. Burroughs, Thomas Jr Corum. Richard N. Miller and Robert L. Stone ABSTRACT: A process for the modification of monomerpretreated keratinous substrates which comprises treating the keratinous substrate with a small but effective amount of a compound selected from the group consisting of phenyl. monoand di-isocyanates and phenyl, monoand di-thioisocyanates.

TREATMENT OF KERATINOUS SUBSTRATES The present invention relates, in general, to the treatment of keratinous substrates and, in particular, to the provision of novel means for synergistically enhancing the physical properties of a wide variety of keratinous substances, such as typified by human hair, animal hair, wool, and the like.

As is well known, keratinous substrates may be modified physically and/or chemically by suitable processing. Thus, the treatment of human hair for purposes of permanent waving as well as other conditioning constitutes well-established technology, the relevant techniques being described in the published literature, both patent and otherwise. Thus, with reference to the treatment of human hair for purposes of imparting curl thereto, conventional processing involves a multistep procedure, the initial operation comprising solution impregnation of the hair fibers with a suitable reducing medium, the reducing solution treatment serving to effect substantial reduction of the keratin material whereby to convert cystine linkages i.e., disulfide bonds to mercaptan. The desired modification of the fiber material is subsequently effected by treating the keratin mass with a suitable oxidizing solution in known manner. The processing solutions and materials required for the implementation of such techniques are likewise well known in the art, being available commercially in a wide variety of forms. Although keratin-modification methods of the aforedescribed type are exploited to a significant extent on a commercial scale, such methods have nevertheless been found in practice to be subject to one or more disadvantages which tend to detract considerably from their commercial desirability. Perhaps, the primary objection concerns the failure of such processing to provide a final hair set possessed of the requisite form-retention stability, the latter condition being essential as regards any possibility of attaining satisfactory hair flexibility and structural integrity devoid of undesired brittleness, hardness, etc. Other disadvantages found to characterize keratin-modification methodology heretofore provided included, for example, the objectionable tendency to yield a hair product of inferior body, thickness, lustre, etc. In practice, it has also been determined that many of the compositions incident to such processing e.g. permanent wave composition, wave sets and the like, characteristically yield undesired film deposits which exhibit a highly objectionable tendency to flake ofi, dry to a hard friable deposit and/or discolor the hair as well as other physical impairment.

Nevertheless, the failure of the keratin-modification treatments heretofore described to provide a final hair set of optimum structural integrity, i.e., in terms of elasticity, tensile strength, form retention capacity, flexibility. resilience, and the like has proved of paramount importance and continues to challenge the relevant technology.

As a result of the foregoing situation, considerable industrial activity has centered around the research and development of methods and compositions specifically and beneficially adapted for use in connection with techniques devised to enable purposive, predetermined modifications in the properties of keratinous substrates absent detrimental effects upon the strength characteristics of the fiber selected for treatment.

Thus, in copending application Ser. No. 829,097 there is described a multistep procedure for the treatment of keratinous materials whereby to achieve selective modifications in one or more properties, the involved process comprising the sequential steps of 1. reduction 2. rinsing 3. oxidation.

In accordance with such processing, initial reduction of the keratin material is effected by treating same with a reducing solution for a time sufficient to permit substantial reduction of the keratin substrate, the term reduction here connoting the conversion of cystine linkages, i.e., disulfide bonds to mercaptan. Upon completion of the desired extent of reduction, the keratin material is subjected to a thoroughgoing rinsing operation for purposes of completely removing residual reducing agent. intermediate rinsing comprises a particularly critical phase of the overall processing scheme, the improvements and advantages described depending pivotally thereupon. Upon completion of the rinsing step, the keratin material is subjected to oxidation with a solution comprising vinyl type monomer in the presence of free radical-liberating catalyst whereby to attach polymerized monomer segments to the individual keratin fibers.

Another technique for effecting the modification of keratinous substrates is described in copending application Ser. No. 829,095, the salient characteristics of this particular method residing in the use of a highly specific catalyst material, namely persulfuric acid and/or its water-soluble salts. The use of this specific catalyst material obviates any necessity for the use of multistep processing while permitting realization of the desired degree of keratin modification. Thus, the contemplated objectives are achieved by the use of a single processing solution containing as essential ingredients the monomer material and persulfuric acid catalyst.

Yet another technique for effectively modifying the properties of keratinous substrates in that described in copending application Ser. No. 829,096. This particular method entails the significant advantage that polymer grafting can be synergistically enhanced or otherwise augmented by etfectuating the monomer-treating operation in the presence of small but effective amounts of a water-soluble halide salt, i.e., a salt of bromine with a water-solubilizing cation such as lithium, sodium, potassium, ammonium, substituted ammonium, and the like. According to such processing, significant improvements in polymer takeup rate is attainable in the absence of adverse effects upon other properties considered desirable if not necessary in the keratin material.

Dissimilar but nevertheless somewhat analogous keratin treatment methodology is likewise described in the published literature both present and otherwise. in the main, such processing involves as an essential expedient the treatment of wool or similar fabric with a reducing agent, such impregnation treatment being designed to deposit upon and within the fibers effective quantities of such reducing agent, e.g., ferrous sulfate.

in any event, and regardless of the particular method employed for purposes of achieving monomer grafting to the keratin fiber it is nevertheless found, other attendant ad vantages notwithstanding, that the beneficial effects are often vitiated due to markedly suboptimum strength properties and particularly wet strength properties in the keratin product, i.e., reference being made in this regard to tensile strength. The importance of the latter is largely self-evident and becomes manifestly clear when considered in connection with the treatment of garments designed for personal wear. As will be recognized, even minor departures from optimum strength characteristics with such fabrics may suffice to vitiate any practical advantage which might otherwise be obtainable. Clearly and especially with respect to garments designed for external wear, the matter of tensile strength is of vital importance bearing upon the appearance, useful life, etc. of the garment. Considerations associated with structural integrity are likewise of primary importance in connection with techniques specifically adapted to enable the modifications of hair whether of human origin or otherwise; accordingly, in the absence of the requisite degree of tensile strength, the final hair product will inevitably exhibit an untoward resistance to form manipulation, e.g., bending, as well as minimal form retention stability with the consequent tendency to snag, snap,

much in the way of meritorious improvement has characterized such efforts, the overall improvement proves in most instances to be of marginal significance only. Thus, it is usually found in practice that the amelioration of problems associated with structural stability and integrity often leads to deleterious effects upon one or more of the other essential properties desired in the treated keratin material product. In addition, economic considerations alone may well be of such significance as to recommend against a given method thus necessitating resort to less costly albeit inferior techniques.

In accordance with the discovery forming the basis of the present invention, it has been ascertained that processing singularly and beneficially adapted for use in the treatment of keratinous substrates and involving the use of vinyl monomer capable of free radical-induced polymerization may be synergistically modified to advantage and thereby rendered more effective by the employment of a posttreating operation involving the subjection of the treated keratin substrate to a substance selected from a highly delimited class of materials, the latter serving to augment or otherwise enhance the structural integrity and particularly tensile strength of the treated substrate.

Thus, the primary objection of the invention resides in the provision of an improved process for the treatment of keratinous substrates wherein the aforementioned difficulties and disadvantages are eliminated or at least mitigated to a substantial extent.

A further object of the present invention resides in the provision of a process for the treatment of modified keratinous substrates which makes possible the production of a final keratin product having exceptional structural integrity said process being effectively devoid of any tendency to disrupt or otherwise adversely affect the properties desired in the final keratin material selected for treatment.

A still further object of the present invention resides in the provision of a process for the posttreatment of modified keratin substrates, said process having exceptional utility in connection with the treatment of modified fibrous materials constituted wholly or partly of keratin whereby to render same more resistant to adverse environmental effects, such as moisture. heat, and the like.

Other objects and advantages of the present invention will become more apparent hereinafter as the description proceeds.

The attainment of the foregoing and related objects is made possible in accordance with the present invention which in its broader aspects includes the provision of a process for the modification of monomer-pretreated keratinous substrates, said monomer having at least one functional group containing an active or labile hydrogen atom which comprises treating said substrate with a small but effective amount of a compound selected from the group consisting ofphenyl monoand di-isocyanates and phenyl monoand di-isothiocyanates. Otherwise stated, the process of the present invention comprises treating a keratinous substrate, the latter having been previously treated with a solution of the aforedescribed monomer(s) under catalytically induced polymerization conditions with said isocyanate compound. in a further aspect, the present invention pertains to the products produced in accordance with the aforedescribed process.

The posttreatment operation described for use in accordance with the present invention is most effectively implemented subsequent to completion of the keratinous substrate monomer treatment. As will be appreciated, the results contemplated herein in nowise depend critically upon the particular point of time at which such posttreatment operation is effected; accordingly, isocyanate treatment may be carried out immediately subsequent to monomer treatment or some period thereafter. The primary requirement, as will be made manifestly clear hereinafter, is that the polymerized monomer fragment present in the keratin substrate selected for treatment have at least one functional group containing a reactive or labile hydrogen atom.

The keratin fiber selected for treatment should be substantially moisture-free prior to contacting with the isocyanate solution in order to minimize problems associated with moisture-induced decomposition of isocyanate.

The isocyanate compounds found to be particularly benefl cial in the practice of the present invention comprise a rela tively delimited class of materials which may for convenience be represented according to the following structural formula:

wherein X represents 0 or S and n represents a number from 1 to 2 inclusive. It will be further understood that the aforedepicted isocyanate compound may further contain one or more nuclear substituents, the salient limitation imposed being that any such substituent group be substantially devoid of any tendency to detract from the efficacy of the isocyanate compound or to otherwise deleteriously affect the improvements contemplated herein. Thus, said additional substituents include, without necessary limitation, halogen, e.g., chloro, bromo, etc.; alkyl, e.g., methyl, ethyl, propyl, etc., and preferably lower alkyl of one to four carbon atoms; aryl, e.g., phenyl, aralkyl, alkaryl, etc. groups of the aforedescribed type having been found to be substantially innocous as regards efficacious implementation of the subject invention. In fact, and as will be made manifestly clear hereinafter, many of the nuclearly substituted derivatives prove more highly utilitous than the correspondingly nonsubstituted derivatives. In any event, and with respect to hydrocarbon substituents such as alkyl, it is recommended that the carbon content be confined within the lower alkyl range in order to minimize penetrability problems often encountered with the higher carbon-content alkyl groups due primarily to the mere physical bulk of such concatenations of atoms. Such a condition serves to impede or otherwise obstruct intimate contacting of the isocyanate derivative with the keratin substrate with corresponding diminution in overall process efficiency.

Specific representatives of isocyanate compounds found to be particularly effective for use herein include, without necessary limitation, the following:

phenyl isocyanate phenyl thinisocyanutc p-chlorophcnyl isocyanate m-chlorophenyl thiuisocyunuie Lil-phenyl diisocyunute l.4phenyl diisocyanate l.4-phenyl di-thiuisocyanate toluene ZA-diisocyunute 3-chlorol .4 phenyl diisocyamute toluene-2.4-di-thiosocyunute 3-propyl phenyl isocyanate It will be further understood that the present invention contemplates the use of the isocyanate compound in admixture comprising two or more thereof. In this manner, the beneficial properties characterizing each of a plurality of isocyanate components may be exploited in a single instance.

Thus, as previously mentioned, it is of critical importance that the isocyanate compound be capable of intimately con tacting the entire extent of the keratin mass. Since increasing the size of the molecular fragment constituting nuclear substituent of the isocyanate compound correspondingly diminishes ease of penetrability, the less bulky groups, e.g. lower alkyl, are preferred. However, it nevertheless recognized that departures from the foregoing carbon content limitations may be feasible or otherwise dictated in certain instances as would be the case, for example, in utilizing auxiliary ingredients for purposes of promoting solubility and/or penetrability, diffusibility, etc. Thus, such limitation is to be regarded as critical solely from the standpoint of assuring the obtention of optimum results rather than a limitation on operability.

The isocyanate component is preferably introduced, i.e., contacted with the monomer-treated keratin substrate in the form of a solution in an inert, organic solvent in order to achieve the requisite intimacy of contacting. Solution concentration is largely a matter of choice, the salient requirement imposed in this regard being that the isocyanate concentration be tantamount to effective" quantities, i.e., quantities conducive to the obtention of the desired degree of structural modification. Thus, the particular proportions employed may range from a small but effective amount, e.g., a 2-3 percent by weight solution to concentrations on the order of 50 percent by weight and higher. The upper limiting concentration value of isocyanate can of course vary within a relatively wide range and thus nothing critical resides in the selection thereof. Thus, a point will be reached where further increase in isocyanate concentration fails to provide commensurate increase in structural modification and thus a levelling" effect is achieved. This will depend of course on the total quantity of polymer present in the keratin mass as well as the population density of functional groups. In any event, isocyanate solution concentrations on the order of from about 2-3 percent to percent weight are found to provide optimum advantage for the vast majority of treatments.

it is likewise recommended to employ the isocyanate solution in amounts sufficient to yield, on a weight basis having reference to total keratin treated, a value within the range of about 3:l to about :1. Again, the sole requirement imposed in this regard is that the solution be used in effective" quantities, the quoted term having the significance previously assigned. As indicated, the selection of an upper limiting concentration value will be determined in large part by economic considerations, levelling" effects and the like.

In some instances, it may be desirable to avoid the use of more concentrated solutions. When so proceeding, it is advisable to limit the isocyanate concentrate to the lower ranges and merely repeat if necessary contacting of such solution with the keratin material, e.g., with successive replenished solutions. in those circumstances permitting the use of more concentrated solutions, the requisite quantity of isocyanate compound may be introduced by the use ofa single solution, thereby obviating any necessity for the use of plural solution treatments, the latter proving rather burdensome from a materials-handling standpoint. isocyanate-keratin contacting is preferably carried out as stated in inert organic solvent media. The nature of the specific solvent selected is not particularly critical apart from the requirement that such solvent be substantially inert, i.e., in the sense of having no appreciable tendency to interact with the isocyanate i.e., N= C=O group. The solvent material selected should furthermore be capable of swelling the keratin. Thus, suitable solvents include. without necessary limitation, dimethylformamide, dimethyl sulfoxide, N,N-diethyl-firmamide, etc.

The processing contemplated in accordance with the present invention may be effectively carried out in the absence of any requirement for elevated temperatures and, thus, room temperature conditions are admirably sufficient. in fact, elevated temperature may well entail significant disadvantages from the standpoint of solvent volatility, materials handling, effects upon the keratin substrate, and the like. Thus, one of the signal advantages afforded by the present invention relates to the fact that any necessity for the use of severe operating conditions e.g., temperature whereby to achieve optimum keratin modification, is entirely obviated.

Duration of isocyanate-keratin fiber contacting may vary within relatively wide limits. having reference, for example, to the amount of polymer present in the keratin substrate, the overall efficiency of isocyanate-kerating contacting, the concentration of isocyanate in the treating solution, the penetrability or porosity of the keratin mass, etc. Thus, periods ranging from as little as 2 minutes to 24 hours may be feasible in a given situation. The actual period of contacting will likewise depend, of course, upon the extent of keratin modification desired. in some instances, only partial restoration of wet strength characteristics may be desired; thus, the isocyanatekeratin contacting period can be adjusted accordingly.

In actual practice, the fiber to treated may be immersed in the solvent solution of the isocyanate compound for the desired interval under conditions promotive of uniform contacting with the entire keratin mass. Alternatively, the isocyanate solution may be applied directly to the keratin mass as by spraying, mechanical applicator, etc., this procedure being particularly feasible in those instances wherein the keratin fiber is to be partially treated, i.e., only certain, predetermined areas. The present invention is applicable to the treatment of materials constituted wholly or partly of keratin such as offscalp, i.e., nonliving human hair such as would be present in wigs and other forms of headdress, woolen garments, and the like. By virtue of such processing, the specific material subjected thereto is characterized by markedly superior physical properties, for example, garment wearability, resistance to humid environments and the like, while headdress articles so treated are possessed of greatly improved form stability, e.g., curl retention stability, ease of manageability and manipulation, etc.

As mentioned previously, the keratin materials contemplated for treatment in accordance with the present invention contain polymer fragments derived from monomer materials having at least one functional group containing an active or labile hydrogen atom.

Examples of functional groups encompassed by the foregoing definition include OH, NH NRH (R=alkyl preferably containing one to four carbon atoms), COOH, SH etc. Thus, keratin substrate suitable for use in the practice of the present invention include those containing polymer fragments derived by graft polymerization of one or more of the following monomer materials:

acrylic acid mclhacrylic acid acrylamide methacrylamide N-elhyl acrylamidc N-hutyl ucrylamid e Z-hydruxypropyl metacrylalc 3-hydroxypropyl mcthacrylate 2.4-dihydroxybulyl mclhacrylatc N,Npmpylcne-his-tN,N-diisupmpyl mclhacrylamidc N,N'-cthylcne-bis-(N.N'-diethyl) acrylumide It will be understood that the present invention contemplates procedures wherein the polymer fragments derived from a given monomer treatment are subjected to further intermediate processing whereby to modify the functional groups e.g., hydrolysis of polyvinyl acetate thereby converting a portion of same to vinyl alcohol type polymer units.

As will be appreciated, in those instances wherein the keratin substrate has been treated with monomeric materials of the polyfunctional type, e.g., those materials containing more than one vinyl-type grouping, such as N,N-ethylene-bis- (N,N'-diethyl) acrylamide and the like, considerable polymer cross linking may occur supplementary to the predominant graft copolymerization action as a result of the polymeriationinducing oxidation treatment. This result obtains, of course, since monomers of this nature possess more than one group capable of undergoing polymerization under the reaction conditions employed. It will be understood that the present invention contemplates the treatment of keratin substrates containing polymer fragments derived from the interpolymerization of one or more of the aforementioned monomers. in such instances, it is required, of course, that at least one of the monomer materials possess at least one functional group containing an active hydrogen atom, such monomer comprising at least 10 percent on a molar basis of the monomer admixture. No such requirement is imposed as regards the nature of the other monomeric components of the admixture. Thus, suitable comonomers include, without necessary limitation, the following:

dimelhylamidc ethyl methacrylate methyl acrylute butyl acrylate allyl acrylate isobutyl methacrylute 3.4-epoxyhutyl methacrylute JA-butenyl acrylute acrylanitrile, etc.

Again, it cannot be emphasized too strongly that the nature of the comonomeric vinylic compounds employed is of relative unimportance, the critical requirement being the use of the monomer component(a) containing the active hydrogen in at least the minimum proportions stipulated whereby to provide a keratin substrate capable of purposive and substantial modificationv Processing in accordance with the present invention is found to be particularly beneficial when the prescribed keratin posttreatment operation is affected with keratin substrates having been subjected to the monomer treatment operation described in copending applications Ser. Nos. 829,095, 829,096 and 829,097, i.e., in the presence of free radical liberating catalyst or initiator. Catalyst materials suitable for such use and described in such aforereferenced copending applications include, without necessary limitation, tertiary butyl hydroperoxide, acetyl peroxide, cumene hydroperoxide, hydrogen peroxide, alkali metal salts of peroxides, alkali metal and ammonium salts of per-acids such as peracetic acid, perbenzoic acid, persulfuric acid, etc. According to the procedure described in copending application Ser. no. 829,097, particularly beneficial results as regards rate of monomer takeup are obtainable with the use of organosoluble initiator compounds such as typified by cumene hydroperoxide, In any event, selection ofa given catalyst system will depend, inter alia, upon the solubility characteristics of the monomer involved, solvent system employed, etc. Thus, the catalyst material in a given instance may exhibit substantial water-solubility or organo-solubility depending upon the factors mentioned.

In any event, it is of utmost importance to note at this juncture that the particular means employed for introducing the monomer substance into the keratin substrate in the form of polymerized monomer fragments is of secondary importance since the present invention may be advantageously applied in connection with the treatment of keratinous substrates containing polymerized products having functional groups containing active hydrogen. The procedures delineated in copending applications Ser. Nos. 829,095, 829,096 and 829,097 warrant particular mention herein in view of their outstanding capability of providing a keratin substrate possessed of optimum properties in a wide variety of aspects. However, such reference should not be interpreted as being tantamount to limitation thereto. lndeed, the contrary situation obtains since the efficacy of the subject invention extends to monomer-treated keratin substrates characterized as defined as regards polymer content regardless of the particular means availed upon whereby to accomplish such monomer pretreatment. Without intending to be bound by any theory, it is nevertheless postulated in explanation of the improvements made possible by the present invention that the isocyanate treatment involves a cross-linking reaction; thus, it is theoretically possible for cross-linking to occur with the monoisocyanate group by reaction first with the active hydrogen-com taining functional group, e.g., carboxy, followed by reaction with a nuclophilic group of the protein. However, whether this possible reaction mechanism is actually responsible for the increased strength or whether a reduction in the saturation water content of the fibers is the determining factor has not been definitely ascertained.

The process described herein may be effectively applied to a relatively wide variety of keratinous materials including, for example, various types of hair, e.g., camel hair, mohair, horse hair, cattle hair, off-scalp human hair, etc., fabric materials constituted wholly or partly of wool and the like. As is well known, keratin materials are categorized among the proteins containing varying quantities of chemically combined sulfur,

the latter being present in the protein molecule in the form of disulfide groups also referred to as cystine linkages. Thus, the amino acids are linked through amino groups to form long chain structures known as polypetides, the latter in turn being mutually inter-connected through disulfide linkages. Thus, no cording to the procedures described in copending applications Ser. Nos. 829,095, 829,096, and 829,097 the disulfide linkages. i.e., SS bonds are converted into thiol groups attached to polypeptide chains, interreaction of the peroxide initiator and the thus-formed thiol groups culminating in the formation of free radical species. the latter serving as the polymerization initiating agency.

The following examples are given for purposes of iliustration only and are not to be considered as necessarily constituting a limitation on the present invention. In the examples, all parts and percentages given are by weight unless otherwise indicated.

In the following examples, the keratin substrate employed, where human hair, is from brown caucasian human hair (non living) and where wool, 64's Marino dry combed top wool.

The polymer material is introduced into the keratin substrate in the following manner. Single fibers, hair or wool, are immersed in a 6 percent ammonium thioglycolate solution (pH 9) for about 3 minutes, washed in deionized water, and then immersed in a water-alcohol mixture of vinyl monomer (l0 percent) and cumene hydroperoxide (4 percent) for 60 minutes at room temperature. Sufficient alcohol is added to the system to completely solubilize the hydroperoxide and monomer ingredients. The amount of polymer introduced into the fiber is calculated by weight pickup as determined in a dry box. The posttreatment operation is carried out by immersing the thus-treated fiber in a solvent solution of the isocyanate compound having the concentration specified for the time period indicated.

EXAMPLE l The keratin fiber selected for treatment comprises human hair, as described, containing l3.37 percent polymethacrylic acid. Stress-strain properties are determined with respect to the polymer-containing hair fiber both prior to (calibration) and following isocyanate treatment in order to enable a comparative evaluation of the resultant wet strength properties. Calibration is carried out by placing the hair sample on a cellulose acetate tab and immersing same in deionized water at room temperature for a period of l to 2 hours. Thereafter, the hair fiber specimen is stretched to 20 percent of its original length on an lnstron tensile tester at a rate of extension of 0.2 inch per minute. The fiber is then relaxed in water for one hour, dried, out from the tab and weighed. The postrelaxation step serves to restore completely the strength properties of the hair sample to the original, prestretching values. The hair fiber is then treated with a 10 percent solution of toluene-2,4-diisocyanate in dimethyl formomide for 15 minutes at room temperature. The hair sample is again stretched in the lnstron tester in the manner described. The changes in Wet strength properties are calculated by comparison of the data obtained from the calibration and di-isocyanate treatments. Positive percentage values signify increases in the corresponding property. The results obtained, reported as an average of 5 hair fiber samples, are summarized as follows:

EXAMPLE 2 The procedure of example i is repeated except that the keratin substrate employed comprises wool fibers containing 24.23 percent grafted polymethacrylic and while the period of treatment with the percent solution of toluene-2,4-diisocyanate in dimethyl formomide is increased to 30 minutes. The results obtained, reported as an average of 5 hair fiber samples, are as follows:

% increase We HL EXAMPLE 3 lncrease Although the incremental increases in the various wet strength parameters are not as pronounced as in the case of toluene-2,4-diisocyanate, it should be pointed out that the contacting period of but [5 minutes is relatively minimal; nevertheless, significant improvement is obtained. Moreover, when the contacting period is increased in 30 minutes and more, commensurate increase in We, HL, and P is obtained. Accordingly, when utilizing a mono-isocyanate in the practice of the present invention. contacting periods of at least minutes are recommended whereby to assure optimum enhancement in wet strength properties.

EXAMPLE 4 Example 3 is repeated except that the isocyanate compound employed comprises P-chlorophenyl isocyanate. The following results are obtained:

70 lncrease We HL As will be noted by comparison with example 3, the halosubstituted phenyl isocyanate proves somewhat more effective than the corresponding, unsubstituted phenyl isocyanate. Again the time significance of the improvements obtainable are evident by reference to the fact that the period of isocyanate-keratin contacting is but 15 minutes. Moreover, such data represents a more than 50 percent increase in We, for example, when compared to a control sample not having been subjected to isocyanate treatment and otherwise identically processed.

EXAMPLES 5 and 6 Example 2 is repeated except that the isocyanate compounds employed comprise phenyl isocyanate and P- chlorophenyl isocyanate respectively. Improvements similar to those described in example 2 are obtained, i.e., in each case, the wet strength parameters of the wool fiber are enhanced to a significant extent.

EXAMPLES 7- l 2 The general procedure outlined in connection with example I is repeated employing the specific isocyanate and keratin substrate identified:

in each case, significant increase in each of We, HL, and F is obtained comparable in magnitude to the results itemized in example 1.

EXAMPLE 13 Example 1 is repeated except that the hair fiber sample contains 19.37 percent poly (Z-hydroxypropyl methacrylate). The following results are obtained.

70 Increase Again, significant enhancement of wet strength parameters is obtained, such data representing a manifold increase over control samples, processed identically, but omitting the isocyanate treatment. The net change in properties, using as a basis the natural or untreated i.e., nonmonomer treated fiber can be derived by the following empirical equation: X=0.0.859 Yl5.7 wherein X represents the total change from the untreated state and Y the total change from the grafted state. The values reported in table l represent of course changes from the grafted state.

Results similar to those described in the foregoing examples are obtained when the procedures described therein are repeated but employing as the keratin substrate both wool and hair fibers containing polymer fragments derived by the polymerization ofthe following monomer materials acrylic acid acrylamide methacrylamide N/butyl acrylamide ethylene glycol monumethuurylate Z-hydmxypropyl methacrylateacrylic acid/methyl mcthacrylate (40:60 mole ratio) acrylamidelmethyl methacrylate (30:70 mole ratio) methacrylic acid/dimethylamino ethyl methacrylate (50:50 mole ratio) Moreover, similar beneficial modification of monomer treated keratin substrates is obtained when the specific isocyanate compounds exemplified are replaced in equivalent quantities with the following:

toluene-2.4-diisocyanate/phenyl isocyunale (50:50 mole ratio) phenyl isocyzmute/phenyl thioisocyunate (25:75 mole ratio) I .3-phenyl diisocyanate 3-chlorophenyl isocyanate 4-bromophenyl isocyunate 3-prup)l phen tl isocyunute li-chlorol A-pheny] diisocyunute l-ethyl-l 4-phenyl diisocyanate 1.4-phenyl dithioisocyanute The use of such solvents as dimethyl sulfoxide, N,N- dimethylacetamide, etc. in lieu of dimethyl formamide provided equivalent results. Thus, inertness" seems to be the essential critered as regards solvent selection.

The significance of the results reported in the foregoing examples can be readily translated in practical terms; thus, the greater wet strength is manifested in the form of exceptional fiber structural stability e.g.. resistance to strength dissipating or disrupting forces etc., the fiber thus provided being readily and easily manipulated to form stable, arcuate i e., curled configurations.

Several factors have been determined to influence the efficacy of the described process with perhaps the more important being of course the presence of functional groups containing active hydrogen in the polymer as well as the ease of modes of proceeding i.e., time of treatment. concentration of treating solution etc.

One of the salient advantages provided by the present invention relates to the fact that processing in accordance therewith not only enables substantial restoration of wet strength properties but moreover, can actually provide a final keratin produce having wet strength properties vastly superior to the characterizing the untreated state. In this connection note the results obtained in examples 1 and 2. it should be noted that an 18 percent increase in a given property corresponds to complete restoration.

What is claimed is:

1. In a process wherein a keratin substrate is polymerized with a vinyl monomer, said monomer having at least one functional group containing active or labile hydrogen selected from the group consisting of OH, NH -NRH, COOH and SH wherein R represents alkyl of one to four carbon atoms, the improvement which comprises treating said substrate with a small but effective amount of at least one isocyanate compound selected from the group consisting or phenyl monoand di-isocyanates and phenyl monoand dithioisocyanates.

2. A process according to claim 1 wherein said keratin substrate is selected from the group consisting of human hair and wool.

3. A process according to claim 1 wherein said isocyanate compound comprises toluene-2A-diisocyanate.

4. A process according to claim 1 wherein said isocyanate compound comprises phenyl isocyanate.

5. A process according to claim 1 wherein said isocyanute compound comprises P chlorophenyl isocyanate.

6. A process according to claim 1 wherein said isocyanate compound comprises toluene -2,4-dithioisocyanate.

7. A process according to claim 1 wherein said isocyanate compound comprises P-chlorophenyl thioisocyanate.

8. A process according to claim 1 wherein said isocyunate compound comprises phenyl thioisocyanate.

9. A process according to claim 1 wherein said monomer comfprises acrylic acid.

l A process according to claim 1 wherein said monomer comprises Z-hydroxypropyl methacrylate.

11. A produce produced in accordance with claim 1. 

2. A process according to claim 1 wherein said keratin substrate is selected from the group consisting of human hair and wool.
 3. A process according to claim 1 wherein said isocyanate compound comprises toluene-2,4-diisocyanate.
 4. A process according to claim 1 wherein said isocyanate compound comprises phenyl isocyanate.
 5. A process according to claim 1 wherein said isocyanate compound comprises P-chlorophenyl isocyanate.
 6. A process according to claim 1 wherein said isocyanate compound comprises toluene -2,4-dithioisocyanate.
 7. A process according to claim 1 wherein said isocyanate compound comprises P-chlorophenyl thioisocyanate.
 8. A process according to claim 1 wherein said isocyanate compound comprises phenyl thioisocyanate.
 9. A process according to claim 1 wherein said monomer comprises acrylic acid.
 10. A process according to claim 1 wherein said monomer comprises 2-hydroxypropyl methacrylate.
 11. A product produced in accordance with claim
 1. 